GSTR2A mismatch

Under Table 8 of GSTR 9 , the ITC from 2A is autopopulated , & taxpayer have to report ITC As per Books , . You can file the GStR 9 with that differences, any difference the reconciliation shall prepared.

Note : Must have Original copy Invoice & goods receipt Proof in case the bills not reflected in 2A

1. Must have original invoice with stamping
2. Goods should be received
3. Payment should be paid through cheque/online banking within 180days.
Note: Once check his GST number whether he is under regular or composition with invoice date.

that means firstly reconcile the GSTR 2A with books and find the invoice which is extra in our books and which invoice extra in GSTR 2A...
but it is very typically to find.. how can we find ??